The present invention generally relates to apparatus and methods for treatment of airstreams in an adaptive Environmental Control System (ECS) to remove particulates, such as ultrafine particles.
ECSs of various types and complexity are used in military and civil airplanes, helicopter, and spacecraft applications. In aircraft for example, airflow may be circulated to occupied compartments, cargo compartments, and electronic equipment bays. Air containing many pollutants such as particulate matter, aerosols, and hydrocarbons may range in humidity from dry (<2%) to very humid and may be delivered in a heated condition to the cabin from the ECS.
Aircraft occupants are not exposed to a single chemical and/or particulate in isolation, and the effects of co-exposures to multiple chemicals and/or particulates are poorly understood. Exposure duration for crews can be 14+ hours. Crews can routinely be assigned to work a 14 hour duty day without a break. The duty day can be extended if there is a maintenance delay or weather. Some international crews are assigned to work a longer duty day. There are flight safety and security implications for not adequately protecting pilots (who must perform cognitively-demanding safety-sensitive flight duties) and cabin crew (who must maintain cabin safety and security). Specifically, manufacturers are currently required to ensure that aircraft systems are designed to provide—in operation, under normal conditions and during any probable failure—“a sufficient amount of uncontaminated air to enable the crewmembers to perform their duties without undue discomfort or fatigue, and to provide reasonable passenger comfort.” It has been widely recognized by air accident investigators, regulators, and pilot groups that flight safety can be compromised when pilots are exposed to oil-based contaminants in the ventilation air entering from outside the aircraft through the main engine bleeds or APU bleed or other air sources including ground supplies and electric compressors. Requiring pilots to rely on their noses to identify the presence and location of bleed air contaminants prolongs the exposure for the pilots and/or cabin occupants, depending on the location of the contaminant source.
The industry accepted approach to verification of acceptability of aircraft cabin air quality has been to gather air samples through various forms of sample media to capture the range of contaminants that might be present. There are three US Environmental Protection Agency (EPA) methods that are accepted as guidance for sample collection and analysis for volatile and semi-volatile compounds and for aldehyde compounds that may create odor and create irritancy.
The sample methodology is inadequate to fully characterize all compounds with any given method, thus requiring the use of multiple methods. The analyst must also determine—based on equipment availability and laboratory capability—which methods to use.
There is limited information in the public domain related to the concentration of ultrafine particles entering the aircraft cabin during the four phases of flight (taxi, takeoff-climb, cruise, and descent). The Institute of Environment and Health (IEH) at Cranfield University has concluded that there was an association between elevated levels of ultra-fine particulate matter in the cabin air supply and when occupants detected oil odors during flight. Professor Michael Bagshaw has concluded that a level of 500,000 particle counts per cubic centimeter was associated with contamination events.
As can be seen, there may be an ongoing need to interpret real-time air particulate data and provide an indication of when the levels may increase beyond the range of acceptability to enable corrective action.